1. Field of the Invention
This invention relates generally to the field of lasers, and more particularly to lasers for pumping optical amplifiers.
2. Description of the Background Art
Known amplifier systems employ a source laser, an amplifier, and a pump source to transfer energy to the amplifying medium, to generate amplified laser light. The source laser emits a beam of laser light that is amplified as it passes through the amplifier. The energy for the amplification is provided to the amplifier by the pump source, which is typically a laser. A pump laser generally includes a laser medium element, positioned between a high reflector and an output coupler, and a pumping means. The pumping means excites the atoms of the medium element into a metastable state. The relaxation of the excited atoms is accompanied by the emission of light, which is reflected back and fourth between the high reflector and the output coupler, and the growing reflected wave induces the emission of additional light into the reflected wave state. As the wave continues to grow, the output coupler allows a portion of the reflected light to pass as the output beam of the pump laser.
It is obviously desirable that the pump laser be efficient, powerful, reliable, and convenient to set up and operate, but often there is tension between these various design objectives. For example, diode lasers provide a very efficient pumping means and are more durable than lamps, but the output energy of known diode-pumped lasers has been too low for them to function effectively as amplifier pumping lasers. Further, some prior diode-pumped systems require that the pitch of the diode emitters be carefully matched and aligned to the optical path within the media element, reducing convenience of assembly.
More powerful pump lasers exist, but in each case the power increase comes at the expense of one of the other design objectives. For example, more power can be obtained by using gas filled lamps to excite the pump laser lasing medium, but these systems are less efficient, less reliable, and less robust. Additionally, such lasers generally have significant cooling requirements and require a special power service, as opposed to a standard 110V AC outlet.
Thus, there is a need for a laser amplifier system capable of producing an output that is orders of magnitude higher in energy than known diode-pumped systems. It is also desirable that the amplifier system be efficient, reliable, and convenient to set up and operate.